1. Field of the Invention
The present invention relates to the control method of broadcast type communication, and more specifically, it relates to the configuration of a distribution device and its communication control method, for example, adopted when conducting broadcast type communication in the form of packet communication.
2. Description of the Related Art
Broadcast type communication that transmits one segment of data from a sender to a plurality of receivers is widely used. A conventional TV broadcast is one example of such broadcast type communication using electrical waves. Recently, as shown in FIG. 1A, basic demand for 1-to-1 broadcast type communication has increased. The distribution of images and voice by streaming that is conducted over the Internet is such one example. Although the present invention is described below using the Internet as an example, the application of the present invention is not limited to the Internet.
In a packet communication network, such as the Internet, multi-cast or uni-cast communication methods are used to conduct broadcast type communication. FIG. 1B shows a multi-cast broadcast type communication. In multi-cast communications, a sender distributes data to a plurality of receivers by transmitting a packet to prescribed multi-cast addresses and data is distributed to the plurality of receivers by copying/transferring the packet in a network according to prescribed routing information. In this multi-cast broadcast type communication, the load of a network is reduced.
FIG. 1C shows uni-cast broadcast type communication. In the uni-cast communication, 1-to-1 packet communication is conducted between a sender and each of a plurality of receivers, and the same data is transmitted from the sender to the plurality of receivers. In this method, since many communications are simultaneously conducted, the traffic increases, which is a problem.
FIG. 1D shows the merits and demerits of both a multi-cast method and a uni-cast method. Regarding the load of a sender, in the multi-cast method, a packet is transmitted only once in the uni-cast method, since a packet is transmitted to each of the plurality of receivers, the load of the sender increases in proportion to the number of receivers. And the load of a network also increases. However, regarding three items of address management, network control and receiver control, in the multi-cast method, they become complex, while in the uni-cast method, they are simple as in the case of 1-to-1 packet communication.
In this way, in reality, either a uni-cast method or a multi-cast method is used depending on the merits and demerits. This is the problem of selection. In multi-cast method, addresses and routing must be managed, while in a uni-cast method, there is no need for special management and is widely used. The broadcast of images and voice called “web-cast” over the Internet adopts this uni-cast method.
As described above, if in a conventional method, the uni-cast broadcast type communication is adopted, the load of a sender and a network are both heavy. Therefore, a multi-cast method is used in order to reduce the network load. However, in that case, the address management, network control and receiver control become complex, which is another problem.